1. Field of the Invention
The present invention is directed generally to the automatic control of DC motors and, more specifically, to the automatic control of arthroscopic surgical instruments powered by DC motors.
2. Description of the Prior Art
Surgical devices for cutting and abrading tissue come in widely different sizes and configurations, each designed for performance of a particular surgical procedure Each surgical device differs with respect to the speed and torque at which it can safely operate. If a surgical procedure on a patient requires use of surgical devices of differing characteristics, the surgeon must either have separate motorized units for each device or a central unit must be adjusted with each device change. The adjustment of a central unit is a time-consuming operation and one that entails some risk of error with possible damage to the device or injury to the patient.
U.S. Pat. No. 4,705,038 to Sjostrom et al. discloses a single-motor surgical system for operating a set of various surgical devices having different operational limits The system includes a handpiece containing a motor. The handpiece is adapted to alternately receive a proximal portion of each of several surgical devices, each device having an indicator on its proximal portion that denotes its operational limits. The handpiece includes an automatic sensor for sensing the indicator. Discrete electronic controls responsive to the sensor automatically establish the operational limits of the motor in accordance with the respective surgical device received by the handpiece.
A disadvantage of the system disclosed in U.S. Pat. No. 4,705,038 is that the discrete electronic circuit which provides the system control has limitations with respect to the degree of precision with which the motor can be controlled Additionally, the discrete electronic circuit is not easily or inexpensively modified to operate additional surgical devices each of which has distinct operating limits. Accordingly, the need exists for a system which can provide enhanced control capabilities and which can be easily and inexpensively adapted to accommodate various types of surgical devices.